Me. Rev. Stat. tit. 35-A, § 716

A public utility shall keep a record of every customer complaint and retain that record for a period of 10 years from the date of final resolution of the complaint and shall make all records of customer complaints readily available to the commission for examination. The commission may adopt rules to implement this section. Rules adopted pursuant to this section are routine technical rules as defined in Title 5, chapter 375, subchapter 2‑A.